/*
 * Copyright 2013 Maurício Linhares
 *
 * Maurício Linhares licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */

package com.github.mauricio.async.db.postgresql.parsers

import com.github.mauricio.async.db.postgresql.messages.backend.{RowDescriptionMessage, PostgreSQLColumnData, ServerMessage}
import com.github.mauricio.async.db.util.ByteBufferUtils
import java.nio.charset.Charset
import io.netty.buffer.ByteBuf

/**

RowDescription (B)
Byte1('T')
Identifies the message as a row description.

Int32
Length of message contents in bytes, including self.

Int16
Specifies the number of fields in a row (can be zero).

Then, for each field, there is the following:

String
The field name.

Int32
If the field can be identified as a column of a specific table, the object ID of the table; otherwise zero.

Int16
If the field can be identified as a column of a specific table, the attribute number of the column; otherwise zero.

Int32
The object ID of the field's data type.

Int16
The data type size (see pg_type.typlen). Note that negative values denote variable-width types.

Int32
The type modifier (see pg_attribute.atttypmod). The meaning of the modifier is type-specific.

Int16
The format code being used for the field. Currently will be zero (text) or one (binary). In a RowDescription returned from the statement variant of Describe, the format code is not yet known and will always be zero.
  *
  */


class RowDescriptionParser(charset: Charset) extends MessageParser {

  override def parseMessage(b: ByteBuf): ServerMessage = {

    val columnsCount = b.readShort()
    val columns = new Array[PostgreSQLColumnData](columnsCount)

    0.until(columnsCount).foreach {
      index =>
        columns(index) = new PostgreSQLColumnData(
          name = ByteBufferUtils.readCString(b, charset),
          tableObjectId = b.readInt(),
          columnNumber = b.readShort(),
          dataType = b.readInt(),
          dataTypeSize = b.readShort(),
          dataTypeModifier = b.readInt(),
          fieldFormat = b.readShort()
        )
    }

    new RowDescriptionMessage(columns)
  }

}
